propeller feathering while ground run
 

Hello ALL.
So to begin. I purchased a field overhauled front engine, IO360C, and replaced the baffling to install it into the rear position. So after installing the engine I was trying to get the fuel system adjusted. I found that during run-up, about ten minutes, the propeller went to feather! I checked the prop rigging and replaced the prop governor. Call a local prop shop, East Coast Prop, Lancaster, Pa. The tech told me it sounded as though the governor was not getting enough oil? The oil pressure was only 30 PSI. And that the latching pin maybe be the problem, but he didn't think so?? The engine had only run for about 1.5 hours since overhaul, I checked the oil condition, which was black as coal? I drained the oil and replaced the filter. Cut the filter open and found some fine grit. I'm thinking that the the case was NOT cleaned properly before reassembling. So I contacted TCM and asked their Tech about the problem. He told me that the "Transfer bearing" maybe clogged or maybe not installed correctly? The bearing hole not aligned with the crankshaft? I also did the pressure check of the prop governor ports. Suppose to be 20-50 PSI, mine was just at 20 PSI, minimum pressure! I removed the pan, thinking it was full of contaminates? Some grit/sludge was in the bottom. While the pan was removed I found a chunk of gasket or solid sludge in the pickup oil screen! Removed the chunk, run the engine---SAME FEATHERING problem? Any thoughts???
Thanks as always!
Regards, BILLS

Sorry to hear of your troubles, BILLS.

Since the prop hub is hydraulic, and requires oil pressure to move the blades to a lower AOA (higher rpm), we can assume the prop hub is not getting the required oil pressure, for some reason, after it warms up.
If the prop hub fails to receive enough oil pressure, the blades will rotate to a higher AOA (lower rpm) until they hit the feathering pins, or "stops".

Since your prop blades go to un-commanded full feather, it would seem to me the pins are not rigged correctly. There is no "auto-feather" on these props! The pins shouldn't release until the prop control lever is in the feathering gate position. We don't want our prop blades going to feather without pilot input, because what if we want to air start? Lets say a tank ran dry, so you switch tanks, and now the engine has fuel again. With the prop windmilling, it will start right back up once it has fuel pressure. Feathered, we'd be hoping the starter and battery were up to the task of turning the motor fast enough to start while the blades are in feather.

IIRC, the props must be turning at 600 rpm or greater in order for the feathering pins to release. This keeps the props from feathering when the engine isn't running.

When running the engine, does the prop slowly move to low rpm over a period of time, or does it release all at once? How does the engine's oil pressure reading change over the 10 minutes? After the prop feathers, while the engine is still hot, are you able to manually move the blades out of feather with a prop paddle or such? Do they stay out of feather (ie do the pins function)? These could be a clue...

Black oil normally indicates excessive combustion ring blow-by. The carbon turns the oil black very quickly. Even one bad cylinder can turn the oil black in a matter of hours.

The sludge is what would concern me. That can clog oil passages.

I would drain the oil through a sieve, collect anything you find, and send some oil in for analysis. If you've got a dry/spun bearing, it will show up in the report.

You may consider adding a quart or two of avgas to your oil and warm up the motor before you drain it. Should help it drain more thoroughly.

I would also run a quick compression test on all the cylinders. You didn't mention if the motor had been broken in yet? Hopefully this wasn't just a "spray paint" overhaul!

oil relief?
 

Bill:

I normally have great oil pressure (50 or better in cruise) but last fall I was flying and the front engine was down to the bottom of the green arc. When I landed and powered back, the pressure went to just above zero. The easiest thing to do if you are contemplating low oil pressure is to make sure the relief valve is not scored and the spring is good. On a "new" engine with junk in the oil, I would check the relief valve port for contamination.

My oil pressure issue was caused by a tiny piece of something (non-magnetic) stuck on the seat of the plunger. If the plunger is displaced at all with hot oil, the pressure will be too low.

See the attached picture of my contamination. Once cleaned and put back together - 50 psi hot all day long again.

If that pic is the head of a Q-tip, that piece of debris was tiny! Its amazing the large impact such a tiny piece of junk can have. :eek:

propeller feathering while ground run
 

TO: mshac and TomM.
Thanks guys for your replies/suggestions.
I replaced the oil relief valve plunger with one that was in better condition. Added three washers, but didn't seem to make a difference.
Oil pressure at start up is 40 PSI, and goes to 32-35 PSI after warm-up(10 minutes). At that time the prop slowly goes to feather. Yes I can lock the prop with a paddle back to low pitch. I can hear the latches lock on. Checked the cylinder pressures, cold, all but number 3 and 4 are 78/80 the others 60-62? Did the fuel in oil and check the pressure at the prop governor pad, suppose to be 20-50 PSI, mine is at 20 PSI. The engine only ran for 0.5 hour after overhaul so I'd say NO to break-in.
Thanks again for your questions and suggestions.
Regards, BILLS

BILLS:

When was the motor overhauled? Have you spoken with the mechanic or shop who performed the OH?

Are the cylinders nickel, chrome, or steel? What type of rings were installed?

What did you find when you drained the oil? Did you refill with mineral oil?

I've never seen an overhauled engine turn the oil black in .5 hrs.

And those compressions should all be in the 70's if everything is fresh.

propeller feathering while ground run
 

MSHAC.
No I didn't talk with the mechanic that overhauled the engine, due to argument between him and the owner of the airplane that I got the engine from. Don't know the kind of cylinders or rings. Oil had small bits of rtv and fine grit in the oil filter, and I'm using multi-grade oil. After counseling with other A&Ps I've decided to remove the engine and send it to a reputable engine shop and have it disassembled, inspected, and reassembled. Repairing anything that needs repaired. In the mean time I'm re-installing my old engine. It was running fine before removal, just leaked quite a bit of oil, mostly from the push rod tube, I think?
Thanks for your questions.
Regards, BILLS

BILLS, I support your decision 110%! The expense is unfortunate, but now at least you should know exactly what you have.

Please let us know what is found.

And I think the rear engine leaks oil on half the 337's out there...the repair is to replace the leaking pushrod tube gaskets, which are held in place only by spring pressure from the pushrod tube against the case. Not a hard job, but you do have to remove the valve cover, rocker arm, and push rod. If you do more than one, make CERTAIN everything goes back exactly where it was!

I have seen them go to feather because they get to hot, running a fuel calibration if ran several times it may have gotten hot and lost oil pressure do to get oil so hot it lost its velocity

Sounds like a smart move. Could have anything in any of those passageways. Don’t want to find out with a starved bearing. Check oil cooler in case it also got contaminated. Pushrod tube seal is easy. Been there. Get the tool for the pushrod spring and it’s a snap.

propeller feathering while ground run
 

Thanks guys for the info. I'm pulling the engine today and installing the old one until I get the overhauled engine checked out.
Appreciate ALL you comments/suggestions!
BILLS